It is nowadays a major concern to considerably reduce the emission of various pollutants in the environment. Volatile organic compounds (VOCs) such as formaldehyde and methanol are some of the products that several industries must treat so as to avoid releasing them to the atmosphere. For example, gases containing such products may be generated in the wood or pulp and paper industries. These gases can be generated during the production of wood-based panel products such as oriented strand boards (OSB), or fibreboards such as low density fibreboards (LDF), medium density fibreboard (MDF) or high density fibreboards (HDF) and particle boards. In various other types of industries, such gases emissions containing VOCs are encountered. Such industries include foundries, smelters, petrochemical industries, sugar industries, dental care products industries, polymer industries automotive industries paint industries, glassware industries and mineral wool industries.
Among the technologies proposed so far there is RTO (Regenerative Thermal Oxidizer). However, it has been demonstrated that such a technology can be very costly to install in a plant, and high maintenance fees may be required to operate it. Moreover, such a technology can generate important amounts of smog precursors, which is undesirable from an environmental point of view. RTO relies on thermal oxidization to destroy these emissions. For example, in the wood-based panel industry, dryer or press gases are sent to the RTO where the VOCs (such as formaldehyde, methanol, ethanol, pinenes, limonenes, camphenes, ketones, etc.) are incinerated at very high temperatures of about 800° C. To increase the thermal efficiency of the system, ceramic beds are used to preheat the inlet air prior to combustion. This technology can be effective in the destruction of VOCs, CO and organic particulate. However, RTOs do generate some NOx (smog precursors) and green house gases (GHG) from the combustion of natural gas and other fossil fuels to generate the required temperatures. RTOs are fairly expensive to operate and require a source of fossil fuel. Moreover, inorganic particulate may cause bed fouling. RTOs operate at or close to the melting point of some of these inorganic particulate and once melted, these by-products can permanently adhere to the ceramic bed and cause premature bed failure. Occasional bed burn-out is required to clear the bed of organic particulate and reduce pressure drops. Additional inorganic particulate devices may be required upstream of the RTO.
Bio-filtration is sometimes used for the capture and destruction of particulates and VOCs. Some mesophilic micro-organisms can be well suited for the destruction of easily degradable VOCs. However, such a technology requires high installation costs and a large surface area. Furthermore, since mesophilic micro-organisms are used, there is a limitation in gas stream temperature which requires dilution with ambient air. This results in larger required area. Such a technology also requires very stable operating conditions.